I cant read the tabs because background and tekst are both white. Where can I change these settings in LibreOffice running on a mac
On other OS Appearance can be reached via Menu Tools>Options
On MacOS all settings should be found via Preferences (as directed by Mac-Guidelines).
https://help.libreoffice.org/latest/en-GB/text/shared/optionen/01012000.html
PS: Appearance is a newer name. If your (unknown) version of LibreOffice is older the name may be different.